I haven't read whether or not 'breakthrough' approval carries with it the same rights to use a drug off-label that ordinary approval does. I somehow doubt that it does.
But once we have regular approval for any indication, it seems to me that the oncology community may not care what BP does, or thinks, about Bavi. Assuming the safety profile holds up and a reasonable price, we may see Bavi used as an adjunct or even solo therapy all over the place.
Sort of like the way the alternative energy industry is exploding under our feet.